This thesis presents a range of different experiments all seeking to extend the capabilities\ of molecular spectroscopy and enable new applications. The new technique of cavity-enhanced direct\ frequency comb spectroscopy (CE-DFCS) provides a unique combination of broad bandwidth,\ high resolution, and high sensitivity that can be useful for a wide range of applications. Previous\ demonstrations of CE-DFCS were confined to the visible or near-infrared and operated over a limited\ bandwidth: for many applications it is desirable to increase the spectral coverage and to extend\ to the mid-infrared where strong, fundamental vibrational modes of molecules occur. There are several\ key requirements for CE-DFCS: a frequency comb source that provides broad bandwidth and\ high resolution, an optical cavity for high sensitivity, and a detection system capable of multiplex\ detection of the comb spectrum transmitted through the cavity. We first discuss comb sources with\ emphasis on the coherence properties of spectral broadening in nonlinear fiber and the development\ of a high-power frequency comb source in the mid-infrared based on an optical-parametric oscillator\ (OPO). To take advantage of this new mid-infrared comb source for spectroscopy, we also discuss\ the development of a rapid-scan Fourier-transform spectrometer (FTS). We then discuss the first\ demonstration of CE-DFCS with spectrally broadened light from a highly nonlinear fiber with the\ application to measurements of impurities in semiconductor manufacturing gases. We also cover\ our efforts towards extending CE-DFCS to the mid-infrared using the mid-infrared OPO and FTS\ to measure ppb levels of various gases important for breath analysis and atmospheric chemistry\ and highlight some future applications of this system.
CY - Boulder DA - 2014-08 N2 -This thesis presents a range of different experiments all seeking to extend the capabilities\ of molecular spectroscopy and enable new applications. The new technique of cavity-enhanced direct\ frequency comb spectroscopy (CE-DFCS) provides a unique combination of broad bandwidth,\ high resolution, and high sensitivity that can be useful for a wide range of applications. Previous\ demonstrations of CE-DFCS were confined to the visible or near-infrared and operated over a limited\ bandwidth: for many applications it is desirable to increase the spectral coverage and to extend\ to the mid-infrared where strong, fundamental vibrational modes of molecules occur. There are several\ key requirements for CE-DFCS: a frequency comb source that provides broad bandwidth and\ high resolution, an optical cavity for high sensitivity, and a detection system capable of multiplex\ detection of the comb spectrum transmitted through the cavity. We first discuss comb sources with\ emphasis on the coherence properties of spectral broadening in nonlinear fiber and the development\ of a high-power frequency comb source in the mid-infrared based on an optical-parametric oscillator\ (OPO). To take advantage of this new mid-infrared comb source for spectroscopy, we also discuss\ the development of a rapid-scan Fourier-transform spectrometer (FTS). We then discuss the first\ demonstration of CE-DFCS with spectrally broadened light from a highly nonlinear fiber with the\ application to measurements of impurities in semiconductor manufacturing gases. We also cover\ our efforts towards extending CE-DFCS to the mid-infrared using the mid-infrared OPO and FTS\ to measure ppb levels of various gases important for breath analysis and atmospheric chemistry\ and highlight some future applications of this system.
PB - University of Colorado Boulder PP - Boulder PY - 2014 EP - 319 TI - Techniques in molecular spectroscopy: from broad bandwidth to high resolution VL - Ph.D. ER -